package p2;

import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: YKH
 * Date: 2023-10-24
 * Time: 11:38
 */
public class exp1_3 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int []meno = new int[n+1];
        System.out.println( getCount(n, meno));
    }

    private static int getCount(int n, int[] meno) {
        if(n==1) return 1;
        if(n==2) return 2;
        if(meno[n]!=0){
            return meno[n];
        }
        return getCount(n-1,meno)+getCount(n-2,meno);
    }
}
